The present invention relates generally to the field of audiometric devices. More particularly, the invention relates to a multi-mode audiometric device and auditory screening method.
Language acquisition in infants requires a critical period of hearing capacity, which spans the frequency range of human speech. The critical period extends from birth to about two to three years of age, when infants typically begin to talk with some level of proficiency.
It has however been reported that approximately three to five percent of newborn infants suffer from some degree of hearing impairment. These impairments can be devastating to the social, emotional and intellectual development of the affected infants. Early identification of hearing impairments in infants allows for early intervention to minimize significant speech and language deficiencies.
Infants are, however, usually unable or unwilling to participate in known behavioral auditory examinations. Moreover, delaying auditory screening until infants can verbally respond is often too late for hearing impaired infants and in many instances, results in long term problems.
Federal, state and private agencies have attempted to implement universal auditory screening of infants for over twenty years. A major impediment to the implementation of universal auditory screening of infants has been the cost and complexity associated with the tests. Current infant screening tests are time consuming and require expensive devices and trained specialists to conduct the tests and interpret results. As such, universal auditory screening of infants is presently economically infeasible.
Various entities have developed audiometric devices, which may be usable for screening an infant""s hearing. These existing devices generally fall into one of two categories. Devices in the first category are configured to elicit auditory evoked potentials (AEPs), which are electrical responses of cells within the auditory pathway of the brain to an acoustic stimulus. Such devices typically utilize the non-invasive auditory brainstem response (ABR) test for auditory screening of infants. An earphone provides an acoustic stimulus, specifically a brief click or toneburst, to the subject""s ear. Electrodes attached to the subject""s scalp receive auditory evoked potentials (i.e., response signal(s)) from the scalp, which are recorded as an electroencephalogram waveform. Analysis of these brainwave patterns are used to determine if the auditory system is functioning normally.
Devices in the second category utilize the evoked otoacoustic emission (OAE) test for auditory screening. An earphone provides a brief acoustic stimulus to the subject""s ear. A microphone disposed in the subject""s ear adjacent the earphone receives an OAE signal from the ear, which is recorded as an acoustic signal. Analysis of the OAE waveform provides an indication of the functional integrity of the middle and inner ear, which together comprise the auditory periphery.
A number of limitations exist with respect to existing audiometric screening devices. One limitation is that virtually all of the existing devices are complicated and require extensive training to operate. Another limitation is that separate devices are required to perform ABR and OAE tests. Yet another limitation is that response signals are susceptible to undesirable artifact components and/or noise, which can emanate from the device itself or the subject (e.g., swallowing, grinding of teeth).
It is therefore an object of the present invention to provide a multi-mode audiometric device and auditory screening method that provides simultaneous, comprehensive ABR and OAE testing through a single, portable device.
It is another object of the present invention to provide a multi-mode audiometric device and auditory screening method that significantly reduces response time (i.e., time to receive a response signal) and, hence, test time.
It is yet another object of the present invention to provide a multi-mode audiometric device and auditory screening method that substantially reduces or eliminates synchronous and sampling artifacts.
In accordance with the above objects and those that will be mentioned and will become apparent below, the multi-mode audiometric device in accordance with this invention comprises stimulus generating means for transmitting at least one true random stimulus sequence to a subject""s inner ear; first detection means for detecting at least one AEP signal, the AEP signal having at least a first waveform; second detection means for detecting at least one OAE signal, the OAE signal having at least a second waveform; signal analyzer means for analyzing the AEP and OAE signals, the signal analyzer means including first averager means for reconstructing the first waveform and second averager means for reconstructing the second waveform; and synchronization means for synchronizing the stimulus generating means and the signal analyzer means.
The method of testing the hearing of a subject in accordance with the invention comprises (i) presenting at least one true random stimulus sequence to said subject""s inner ear, (ii) detecting at least one AEP signal, the AEP signal having at least a first waveform, the first waveform including a first set of AEP signal data, (iii) detecting at least one OAE signal, the OAE signal having at least a second waveform, the second waveform including a first set of OAE signal data, (iv) recording the AEP and OAE signals, (v) sampling the first set of AEP signal data by applying a plurality of true random frequencies to the first set of AEP signal data to provide at least a second set of AEP signal data, (vi) recording the second set of AEP signal data, (vii) reconstructing the first waveform from the second set of AEP signal-data, and (viii) averaging the first set of OAE signal data to reconstruct the second waveform.